Goldman Sachs (NYSE:GS) continues to deliver strong operating results and more than just one reason to buy the investment bank. Solid increases in revenues, net earnings and book value all support an investment in Goldman Sachs.

In fact, strong growth in its underlying tangible book value per share and a consolidation of Goldman Sachs' stock price have made the investment bank even more interesting as a long-term investment over the last couple of months.

Resilient business during the financial crisis
One of the companies that weathered the 2008 storm in the financial sector the best was Goldman Sachs. The investment bank was among the first to repay the Tarp bailout funds and also found a $5 billion investment from value investor Warren Buffett who opportunistically used the market panic in 2008 to snatch up Goldman Sachs' shares on the cheap: a convincing endorsement of the bank's long-term value proposition.

Fast forward a couple of years and the financial sector has clawed its way back to a better revenues and earnings profile.

With improving U.S. economic growth and a return to normalcy, banks have still meaningful room to grow their earnings. And this is particularly true for one of the leading investment banks in the country, Goldman Sachs.

GSource: Wikimedia Commons, Goldman Sachs Tower, New Jersey

Strong recovery in financial services benefiting Goldman Sachs
In 2011 Goldman Sachs reported net revenues of $28.8 billion which grew to $34.2 billion in 2013, a plus of 19%. Net earnings applicable to common shareholders, however, rose at a much higher rate of 208% to $7.7 billion.

While 2011 was truly not a good year for Goldman Sachs in terms of profitability, it is good to see that 2011 was just an outlier.

Goldman Sachs' Investing and Lending division can largely be credited with the strong rebound in Goldman Sachs' performance improvements. Net revenues in this important business segment ballooned from $2.1 billion in 2011 to over $7.0 billion in 2013.

Pre-tax earnings, at the same time, rebounded significantly from a loss of $531 million in 2011 to $4.3 billion in 2013. Results in the Investing & Lending division were largely driven by the ongoing rally in the equity markets and higher equity prices.

Healthy performance metrics and shareholder returns
With a normalization of the banking business and improving equity markets providing tailwinds, it comes as no surprise, that Goldman Sachs' book value also grew healthily over the last three years.

From 2011 to 2013 Goldman Sachs has increased its tangible book value per share by 20% to $143.11. Goldman Sachs' first quarter results also highlighted, that the growth in tangible book value per share continues.

Weaker revenues and earnings in 2011 were also reflected in Goldman Sachs' weak return on common shareholders' equity, which stood at just 3.7% in 2011. In 2013, this important financial metric to gauge the profitability of the bank's operations has skyrocketed to 11%.

Final assessment
Goldman Sachs remains a solid bet on an improving banking sector. The bank's track record in growing revenues and earnings in a difficult operating environment induces confidence, that Goldman Sachs can continue its growth in the coming years. With just a slight premium of 14% to its first quarter tangible book of $145.04 per share, Goldman Sachs is not too expensive either.

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Kingkarn Amjaroen has no position in any stocks mentioned. The Motley Fool recommends Goldman Sachs. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.